The present invention relates to an airbag apparatus which is suitably used as a passenger- or driver-side airbag apparatus installed in front of an occupant in a vehicle such as an automobile.
A passenger-side airbag apparatus comprises a container arranged in an instrument panel in front of a front passenger seat, a gas generator for inflating an airbag, the airbag which is folded and accommodated in the container, and a lid covering the container. As a vehicle comes in collision, the gas generator is actuated to supply gas into the airbag, whereby the airbag starts to inflate. As the airbag starts to inflate, the lid is pushed by the airbag to open so that the airbag inflates toward the vehicle cabin. The airbag is provided with a gas inlet for receiving gas from the gas generator. The peripheral edge of the gas inlet is connected to the container.
As described in Japanese Patent Unexamined Publication H04-100754 (incorporated by reference herein), the airbag is folded by a step of first reverse folding both left and right sides of the airbag toward the center, the airbag in this state being called as an interim folded body having a reduced lateral width, and a step of folding the interim folded body into a bellow, the airbag in this state being called as a lump body. Then, the lump body is accommodated in the container.
Hereinafter, the way of folding an airbag disclosed in the publication H04-100754 will be described with reference to FIGS. 11 through 17.
FIG. 11 is a perspective view showing an airbag 1 spread in a plane and a sub container 2. The airbag 1 is an envelop-like object of which the shorter sides 1b are rectilinear and the right and left longer sides 1a are curved in arc-like shape. Formed in the center of a layer on a side opposite to the surface to be arranged to confront an occupant is gas inlet 3 for receiving gas from an inflator. Also formed in the layer are gas outlets (vent holes) 4 for buffering impact on the occupant when the occupant collides with the deployed (fully inflated) airbag. Numeral 5 designates rivet holes. The sub container 2 has a bottom face with holes 6 for passage of gas from the inflator.
As shown in FIG. 12, the airbag 1 is spread in a plane in a state that the sub container 2 is connected to the airbag 1. Then, as shown in FIG. 13 and FIG. 14 (sectional view taken along a line XIV—XIV of FIG. 13), portions along the longer sides 1a are folded inside the airbag 1 to make the width of the airbag 1 slightly smaller than the width of the sub container 2, so as to form an interim folded body.
Next, as shown in FIG. 15 (side view taken from a line XV—XV of FIG. 13), the interim folded body is repeatedly folded into a bellow to make valley and mountain folds 7 in directions perpendicular to the rectilinear longer sides 1a′ of the interim folded body. As shown in FIG. 16, repeatedly folded portions are piled on each other to form a lump body and the lump body is accommodated in the sub container 2 (FIG. 17).
In this publication H04-100754, the folded airbag is accommodated in the sub container 2 and the sub container 2 with the airbag is accommodated in a main container (not shown). However, the sub container may be omitted and in this case, the folded airbag is directly accommodated in a container.
In the conventional passenger-side airbag device, the airbag 1 is folded so as to form the lump body. The peripheral edge of the gas inlet 3 of the airbag 1 is connected to the sub container 2. Assuming the area of the airbag 1 about the periphery of the gas inlet 3 is composed of two area: a windshield-side area 1A connected to a windshield side 2A of the sub container 2 and an occupant-side area 1B connected to the occupant-side 2B of the sub container 2, the windshield-side area 1A and the occupant-side area 1B are equal in length.
Therefore, when the airbag 1 is inflated (deployed) by gas from the inflator, the airbag 1 is deployed such that a vehicle-front side portion i.e. the windshield side portion and a vehicle-rear side portion i.e. the occupant side portion of the airbag are substantially symmetrically inflated.
It was found from various studies that the smooth deployment of the airbag may be obtained by such a structure that the front portion (vehicle-front side portion) of the airbag is inflated earlier than the rear portion (vehicle-rear side portion) of the airbag, but of course, it depends on the layout of the cabin and the arrangement angle of the instrument panel of the vehicle and the arrangement of the airbag apparatus.
It is an object of the present invention to provide an airbag apparatus in which a front portion (vehicle-front side portion) of an airbag is inflated earlier than a rear portion (vehicle-rear side portion) of the airbag.